Grinding apparatus

ABSTRACT

A processing apparatus adapted to reduce the aggregate size of particles comprises a rotatable shaft concentrically mounted in a casing to form an annular channel in which the particles are received. A plurality of grinding rolls are disposed in said channel, at least one of said rolls being connected to the shaft for rotation therewith. Various sizes and arrangements of rolls are disclosed, all adapted to provide a shearing action on said particles upon rotation of said shaft relative to said casing.

O Umted States Patent 1151 3,679,141 Bristol [451 July 25, 1972 [54] GRINDING APPARATUS 2,055,956 9/1936 Wells ..241/120 X [72] Inventor: Bertram W. Bristol, 71 Newman Ave., 1656l64 1,1928 Bwgaxd H X v NJ 07044 302,817 7/1884 Ba1ley ..241/103 1,380,112 5/1921 Middelboe ..241/103 [22] Filed: July 29, 1970 Primary Examiner-Robert L. Spruill [21] PP -z 59,115 Attorney-James and Franklin [52] us. c1 ..24l/l06, 241/109, 241/1 10, [57] ABSTRACT 1 241/1 13 A processing apparatus adapted to reduce the aggregate size [51] Int. Cl. ..B02c 4/10, B02c 15/08 of particles comprises a rotatable shaft concentrically [58] Field of Search ..241/107-109, 111, mounted in a i g to form n annular channel n which h 241/113, 114, 118, 119, 120, 123,124, 126, 122, particles are received. A plurality of grinding rolls are 144, 160, 228, 252, 103, 106, 110, 172 disposed in said channel, at least one of said rolls being connected to theshafl for rotation therewith. Various sizes and Rderenm Cited arrangements of rolls are disclosed, all adapted to provide a shearing action on said particles upon rotation of said shaft UNITED STATES PATENTS relative to said casing 1,589,302 6/1926 Middelboe ..'241/130 X 22 Claims, 5 Drawing Figures GRINDING APPARATUS The present invention relates to a grinding or milling apparatus particularly well adapted for use with printing ink dispersions.

In the manufacture of printing inks, the raw product comprises various varnishes, oils, resins, pigments, additives and other components in a rather viscous non-uniform suspension. This suspension must be converted into a uniform homogeneous dispersion in order to be acceptable as a finished printing ink. Moreover, the particle size of the various solid components must be considerably reduced and uniformly dispersed within the vehicle. Premixing accomplishes some dispersion and reduction in particle size but a printing ink of satisfactory quality normally requires a certain amount of grinding or milling.

Various devices have been devised for milling pigment dispersions, the most common of these in the printing ink industry being the roll mill. Grinding and dispersion is accomplished in a roll mill by the shearing action produced by the relative movement of two surfaces disposed in close proximity to each other. In a single roll mill, the raw mixture is introduced into a hopper above the roll and is passed between the roll surface and a stationary vane bar pressed against the roll. The finished product is scraped from the roll downstream of the vane bar. While this structure is relatively simple and operation and maintenance is relatively inexpensive, the shearing action produced is unsatisfactory, particularly for compositions of high viscosity. Thus, single roll mills have found use primarily as a finishing or blending device or in the processing of mixtures containing relatively soft grinding pigments.

The multiroll mill is widely used for the processing of printing ink pigment dispersions and other products of intermediate and high viscosity, The most commonly employed three-roll mill utilizes the shearing action at the two nips formed by three rolls driven at different speeds. The mixture is fed into the nip of the first two rolls and is carried by the center roll into the nip area defined bythe more rapidly moving third roll to which it adheres. Here again the final product is removed from the third roll by a scraper or takeoff knife. A shearing and grinding action takes place at the interface of the first and second and second and third rolls. The degree of particle size reduction is determined by the roll clearances at these interfaces, the clearance at the second interface normally being smaller than that of the feed rolls so as to further disperse the particles. The five-roll mill subjects the dispersion to two additional grinding and shearing interfaces and operates in a manner identical to the operation of the three roll mill.

The multiroll mill has many disadvantages, the most significant of which are its complexity and cost. The quality and output of such mills is determined by the roll clearances. Thus, for good quality the rolls must be finished to tolerances of the order of 0.0002 inch. However, evenwith rolls machined to close tolerances, setting of the proper clearances is difiicult because during operation the mill frame, as well as the rolls, are subject to severe elastic deformation. Variance in roll clearance, particularly at the feed rolls, may result in an inferior product. This is because the feed rolls function primarily as crushing rolls for oversize particles and aggregates, and the succeeding rolls serve primarily to subject the crushed film to viscous shearing forces within the suspending medium. If the mixture contains particles significantly. larger than the clearance at the feed rolls, they will not be drawn into the apparatus until the volume above the rollsis small, .at which time they will enter the nip and may be compacted into a dry localized mass which may carry through the subsequent rolls.

Another drawback of the roll mill is that speed and thus Thus, it may be necessary to add solvent during the milling process.

Enclosures for the mill may reduce evaporation and splattering but such devices are rarely used because they are cumbersome and obstruct the view of the milling process.

The use of a take-off knife also involves several significant problems. The knife blade must be accurately spring biased against the terminal roll at a pressure which is high enough to remove all the material but low enough to prevent grinding of the blade, the latter resulting in excessive power consumption and the formation of burrs on the blade, these in turn tending to-introduce airinto the mixture. Because the correct pressure setting is a function of'the viscosity-of the mixture, the roll speed and the clearance setting on the terminal rolls, frequent adjustments are generally required.

Moreover, the take-01f knife is a prime source. of contamination in the form of abraded steel introduced into the composition, particularly at high pressure blade settings.

devices have been found to be unsatisfactory either because quality and output is limited by the tendency of low and medithey impede the proper operation of the device or else are impractical. As a result, operators must handle the apparatus with considerable care to avoid serious injury.

By contrast, the apparatus of the present invention is rather inexpensive to manufacture, safe and, simple to operate and maintain, and designed to provide extremely good grinding and shearing action on a pigment dispersion.

Accordingly, it is a primary object of the present invention to design a processing apparatus for reducing the aggregate size of particles which-is simple and inexpensive to operate and maintain and provides a relatively high uniform output of particles of reduced size.

More particularly, it is an object of the present invention to provide a grinding and dispersion apparatusv which is completely enclosed andis adapted to uniformly grind and disperse particles suspended in vehicles of varying viscosities.

It is another object of the present invention to design a processing apparatus adapted to provide roll mill type shearing action on pigment dispersions .and produce a finished product of improved quality without the use of a take-off knife.

It is yet another objectof the present invention to design a dispersion apparatus adapted to turn out in a single pass a pigmerit dispersion of a quality equivalent to the quality produced by several passes over a conventional roll mill.

It is still a further object of the present invention-to provide a processing apparatus for pigment dispersions wherein the amount of material processed is not limited by its viscosity and wherein high outputs are attainable without a deterioration in quality.

It is yet another object of the present invention to provide a dispersion apparatus which introduces virtually no air or contamination into the mixture, and in which solvent evaporation is virtually nonexistent.

To these ends the present invention comprises a rotatable shalt concentrically mounted in a casing. Aplurality of grinding rolls are disposed within the annular channel defined between the shaft and the inner wall of the casing. In one embodiment the shaft is provided with arcuate grooves each adapted to receive and retain a freely rotatable grinding roll having a diameter larger than the channel width. A second embodiment provides rolls of a diameter smaller than the channel width disposed in free-floating contiguous relationship within the channel, alternate rolls being in substantially abutting relationship with the shaft and the inner wall of the casing, respectively. A third embodiment employs rolls having a diameter spanning the channel interspersed with smaller rolls wedged therebetween against the shaft. In all three embodiments, at least one of the grinding rolls is connected to the shaft so as to rotate therewith; in the first embodiment the shaft grooves accomplish this, while in both the second and third embodiments at least one of the grinding rolls is connected to the shaft by means of a collar mounted fast on the shaft.

The casing is provided with an inlet port at one end and an outlet port at its other end. The raw mixture is pumped into the channel at the inlet port and the shaft is rotated at high speed. The grinding rolls are accordingly forced to rotate (both with the shaft and about their own axes) and provide an extremely efficient shearing and grinding action at the interfaces between contiguous rolls, between the rolls and the shaft and between the rolls and the inner wall of the casing. The final product is dispensed from the outlet port into a container.

To the accomplishment of the above, and to such other objects as may hereinafter appear, the present invention relates to a grinding apparatus as defined in the appended claims and as described in this specification taken together with the accompanying drawings in which:

FIG. 1 is a front elevational view of the grinding apparatus of the present invention;

FIG. 2 is a partial vertical cross-sectional view of the apparatus of FIG. 1; and

FIGS. 3-5 are cross-sectional views taken through the line A-A of FIG. 2 and illustrating three exemplary embodiments of the present invention.

Referring now to FIG. 1, it will be seen that a grinding assembly generally designated is mounted on a frame 12 which is shown mounted on rollers 14 to provide mobility. A hopper 16 is provided at the inlet end of the assembly and a spout 18 is provided at the outlet end thereof.

As best shown in FIG. 2, assembly 10 comprises a cylindrical casing 20 mounted longitudinally on frame 12 by suitable bracket means 22. A shaft 24 is mounted concentrically within casing 20 to form therebetween an annular channel 25. Shaft 24 extends from casing 20 at its outlet end (the left end as viewed in FIG. 2) and terminates short of its inlet end. The extended portion of shaft 24 is journalled in a bearing 26 which extends from frame 12. Bearing 26 is in turn secured to a face plate 28 and adapted to seal the open outlet end of casing 20.

A pump 30 at the inlet end of casing 20 is adapted to pump the raw mixture from hopper 16 through pipefitting 32 into casing 20. Accordingly, a coupling member 34 threadingly en- 7 gages pipe fitting 32 and casing 20 to provide a fluid passage therebetween. As best shown in FIG. 1, pump 30 is driven through a chain drive 36 by a suitable electric motor generally designated 38 mounted on frame 12.

A second electric motor generally designated 40 is mounted at the other end of frame 12 and is adapted to drive shaft 24 by means of pulleys 42 and 44 and belt 46. A cylindrical sleeve 48 is mounted in spaced surrounding relation to casing 20 and is secured to frame 12 by a suitable bracket 49 thereby to provide an annular channel 47 for the flow of cooling fluid over casing 20. Accordingly sleeve 48 is provided with flanged portions 50 and 52 at either end. Flanged portion 50 is secured to a correspondingly flanged portion of coupling member 34 at the inlet end of casing 20 and flanged portion 52 is secured to a flange member 54 which is fast on casing 20 at its outlet end. Fluid connectors 56 are secured to apertured portions of casing sleeve 48 to allow for the circulation of cooling fluid into and out of channel 47, as indicated by the arrows 57 in FIG. 2.

The flow of material through the processing apparatus is indicated by arrows 59 in FIG. 2. As there shown, the mixture is deposited in hopper l6 and enters the inlet 31 of pump 30. It is then pumped through pipe fitting 32 and coupling 34 into casing 20, it is forced through the annular channel 25 defined between shaft 24 and the inner wall of casing 20, and it emerges at outlet spout 18 at the other end of casing 20. The grinding and dispersion process takes place along the length of channel 25 as a result of the rotation of shaft 24 within casing 20. For this purpose a plurality of grinding members in the form-of narrow circular pins or rolls generally designated 58 are longitudinally disposed within channel 25. The dimensions and disposition of rolls 58 determine the mode and effectiveness of the grinding and dispersion process along channel 25.

Three exemplary embodiments of grinding roll arrangements are illustrated in FIGS. 3, 4 and 5 respectively.

In the embodiment of FIG. 3 rolls 58 comprise two sets of rolls 60 and 62, respectively. Rolls 60 are of a diameter substantially the same as the width of channel 25 and are therefore in substantially abutting relationship with both the inner wall of casing 20 and the outer surface of shaft 24. The second set of rolls 62 have a substantially smaller diameter than rolls 60 and are interspersed between successive rolls 60 in contiguous relationship. As shown in FIG. 3 rolls 62 are thus wedged against shaft 24. It will be apparent that each roll 60 has four potential grinding and shearing interfaces, namely, its interfaces with rolls 62 on either side, its interface with the inner wall of casing 20 and its interface with the outer surface of shaft 24. In addition each roll 62 has a potential grinding interface with shaft 24. It will be apparent that shearing action at these interfaces depends upon relative movement of the contiguous surfaces. If rolls 60 and 62 are all disposed in free floating relationship within channel 25, rolls 60 will function as roller bearings against casing 20 and shaft 24, and thus these interfaces will provide no shearing action.

In order to provide relative movement and thus shearing action at all interfaces, rolls 60 and 62 must be forced to translate either with shaft 24 or with casing 20 relative to the other. In the present embodiment means are provided to force the grinding rolls to revolve within channel 25 around the axis of shaft 24 as shaft 24 is rotated. This means is best shown in FIG. 2. As there illustrated a plurality of spaced collars 64 are mounted fast on shaft 24, and extend radially from shaft 24 a substantial distance into channel 25, thereby dividing channel 25 into a plurality of longitudinally spaced compartments generally designated 66. FIG. 2 shows four spaced collars 64 defining three compartments 66. It will be apparent, however, that more or fewer compartments may be provided depending upon the desired operative length of casing 20 and the length of the individual rolls 58. Collars 64 are spaced from the inner wall of casing 20 to provide a small clearance 67 for the flow of the mixture from one compartment to the next. Rolls 58 are disposed within each compartment and extend substantially from collar to collar. Each collar is provided with two recesses or keyways 68 facing each compartment, the recesses preferably being disposed apart. Accordingly, in the embodiment of FIG. 3 two of the larger rolls 60 disposed 180 apart in each compartment are longer than the others and are adapted to be rotatably received at either end in the recesses 68 of the collars 64 defining the compartment 66. One such roll designated 70 is shown in each of the three compartments 66 in FIG. 2. Thus, as shaft 24 is driven at high speed by motor 40, rolls 70 are adapted to drive all the grinding rolls 60 and 62 in a circular path within annular channel 25 at the peripheral speed of shaft 24. The mixture is accordingly subjected to a severe mixing, grinding and shearing action as it is pumped through channel 25. This is accomplished as a result of the frictional and inertial resistance of the mixture to the motion of the rolls within channel 25. While the fluid mixture is to some extent carried in a ring-like path around channel 25 within spaces 72 between consecutive rolls 60 and spaces 73 between rolls 60 and 62 the inertia of the fluid tends to draw it through the slight clearances at the interfaces between rolls 60 and 62, rolls 60 and casing 20, rolls 60 and shaft 24,'and rolls 62 and shaft 24. It will also be noted that as rolls 60 move along the inner wall of casing 20 rotational motion will be imparted to those rolls (preferably including the collar-engaging roll or rolls 70) at their interface with the casing. Thus if shaft 24 is driven clockwise, rolls 60 will tend to rotate counterclockwise at the same time as they are revolving about the axis of shaft 24. However, the surface of shaft 24 will provide frictional resistance to this rotational motion. Since all the rolls are freely rotatable within channel 25, rolls 60 will be stabilized at a rotational velocity such that there is relative movement at both the casing and the shaft interfaces. On the other hand rolls 62 will tend to rotate clockwise as a result of the frictional forces imposed by rolls 60 on either side thereof as a result of their counterclockwise rotation. Again there will be frictional resistance to the clockwise rotation of rolls 62 provided by shaft 24. As a result rolls 62 will be stabilized at a rotational velocity such that there is relative movement at the shaft interface and the interface with adjacent rolls 60. Thus, it can be seen that fluid being drawn through the clearances at any of the above enumerated interfaces will be subjected to severe shearing forces in the nature of roller mill shearing action. However, unlike a conventional roller mill, the present apparatus is adapted to force the mixture through the clearances at these interfaces at high speeds as a result of the inertia of the mixture itself.

The resulting grinding and shearing action is best explained with regard to the relative motion of the fluid, the rolls, the casing and the shaft. Thus, neglecting for a moment the inertia of the fluid, the counterclockwise rotation of rolls 60 would normally tend to draw fluid in a counterclockwise direction through its interfaces with casing 20, shaft 24 and rolls 62. Likewise the clockwise rotation of rolls 62 would normally tend to draw fluid in a clockwise circulation through its interfaces with rolls 60 and shaft 24. Accordingly, the fluid in space 73 would tend to be drawn in two different directions with respect to the axis of shaft 24 namely, counterclockwise through the clearance between roll 60. and casing 20 into the next space 73'and clockwise through the clearance between roll 60 and roll 62 into space 72. The fluid in space 72 would likewise tend to be drawn in two different directions namely, clockwise through the clearance between roll 60 and shaft 24 into the next space 73 on one side and counterclockwise through the clearance between roll62 and shaft 24 into the next space 72 on the other side. It will be apparent that in the present apparatus there is superimposed upon the foregoing fluid flow, the inertia of the fluid to the clockwise rotation of shaft 24 and the clockwise revolution of rolls 60 and 62 within channel 25. The resulting fluid dynamics of the grinding and dispersion process is not accurately known, but it is believed that at high rotational speeds the mixture is forced under great stress and at high velocities through all interfaces in a counterclockwise direction (assuming shaft 24 is driven clockwise), resulting in tremendous shearing and grinding forces on the mixture. Moreover,'because fluid is continually pumped into channel 25 it completely fills spaces 72 and 73. As a result the dispersed mixture is further mixed within spaces 72 and 73 after each traverse through a shearing interface.

Large particles will tend to remain within spaces 72 and 73 7 until they are broken up by the high velocity fluid vortices generated within these spaces. Moreover those large particles which are drawn through an interface will be subsequently dispersed in fluid form throughout the mixture. Thus, dry localized compacted masses are completely eliminated.

If rolls 60 and 62 are disposed contiguously as shown in FIG. 3, it will be apparent that the smaller rolls 62 will remain wedged against shaft 24 by the larger rolls 60 notwithstanding the centrifugal force tending to throw them outwardly against the inner wall of casing 20. However, if the clearances are large (either initially or as a result of substantial wear), rolls 62 may tend to drifi outwardly toward the inner wall of casing 20. Accordingly it may be desirable to form collars 64 with an undercut portion (not shown) adjacent to shaft 24 adapted to accommodate rolls 62 and retain them in abutting relationship with shaft 24. If this expedient is adopted, rolls 62 should of course be longer than rolls 60 so as to be received at both ends in the undercut portions of collars 64.

The embodiment illustrated in FIG. 5 is similar in operation to that of FIG. 3. Again two sets of rolls are disposed in contiguous free floating relationship in channel 25. The first set of rolls 74, comprising every other roll, is in substantially abutting relationship with the inner wall of casing 20 and the second set of rolls 76 is disposed in substantially abutting relationship with shaft 24. All rolls have diameters substantially smaller than the width of channel 24, thereby defining spaces 78 and adjacent casing 20 and shaft 24 respectively. FIG. 5 shows all rolls of equal diameter but it should be noted that various arrangements using varying size rolls are within the scope of this embodiment.

As with the embodiment of FIG. 3, two rolls spaced apart are keyed to shaft 24 via recesses 68 in collars 64. In operation if shaft 24 is driven clockwise the rolls in the outer set 74 are rotated counterclockwise as a result of their frictional engagement with the inner wall of casing 20. As a result the rolls in the inner set 76 are rotated clockwise. (This rotation, however, is at a somewhat lower velocity than that of rolls 74-because of the frictional resistance at the interface with shaft 24.) Shearing and grinding action thus takes place at the interface between rolls 74 and 76, between rolls 74 and the inner wall of casing 20, and between rolls 76 and shaft 24. The mixture is accordingly subjected successively to shearing and grinding at the foregoing interfaces and mixing and dispersion within spaces 78 and 80 in a manner similar to the operation of the embodiment of FIG. 3.

FIG. 4 illustrates an arrangement utilizing the basic concept of the present invention but somewhat different structurally from the embodiments of FIG. 3 and FIG. 5. As there shown, shaft 24 is provided with spaced arcuate grooves 82 around its circumference. Grooves 82 are adapted to receive and retain rolls 84 in freely rotatable relationship. Rolls 84 have a diameter such that they span the width of channel 25 and are received in grooves 82 with only a slight clearance. It will be apparent that in operation when shaft 24 is driven clockwise, rolls 82 by virtue of their frictional engagement with the inner wall of casing 20 are caused to rotate counterclockwise. Again, however, the frictional resistance of the surface of grooves 82 to this motion slows the rotation of rolls 84 to a rate such that there is relative motion at the roll interface with both casing 20 and shaft 24. It will be apparent that in this embodiment, the recesses 68 in collars 64 are unnecessary, all rolls 84 being connected to the shaft 24 for rotation therewith. Thus the mixture is subjected to extreme shearing and grinding forces at both of these interfaces. Again considerable mixing and dispersion takes place in spaces 86 betweenconsecutive rolls 84.

In all of the foregoing embodiments the mixture is forced axially along channel 25 while at the same time being mixed, dispersed and ground by the grinding rolls 58. The quality of the processed dispersion will, of course, be a function of the properties of the raw mixture, the speed of rotation of shaft 24, the clearances at the various grinding interfaces, and the diameter and operative length of the annular channel 25. It has been found that a typical assembly is adapted to turn out approximately 1,000 pounds per hour of good quality finished lithographic ink with a shaft rotation of approximately 1,000 rpm starting with a medium body lithographic black base. The particle size and gloss of the finished ink is at least equal in quality to that produced by three or more passes over a conventional roll mill.

As illustrated by the arrows 59 in FIG. 2 the final product emerges from casing 20 at outlet spout l8. Depending upon the properties of the starting mixture the finished dispersion may emerge as a viscous fluid or in the form of dry, thin shavings. A take-ofi knife is unnecessary since the mixture is continually pumped through casing 20 and very little, if any, of that material adheres to the shaft, the casing or the grinding rolls. As a result the final product contains very little, if any, contamination in the form of abraded steel.

If shaft 24 is driven at very high speeds, the heat generated may make it necessary or desirable to provide a conduit through the center of shaft 24 for the passage of additional cooling fluid.

The apparatus described herein is inexpensive to manufacture and maintain and is simple to operate. It is adapted to provide extremely uniform, uncontaminated, high quality dispersions of various inks, pigments or other mixtures in a single pass.

, While only a limited number of embodiments of the present invention have been disclosed herein, it will be apparent that many variations may be made therein, all within the scope of this invention as defined in the following claims.

I claim:

1. A processing apparatus for reducing the size of particles comprising a casing having an inlet and an outlet, a body movably mounted within said casing and spaced from the inner wall thereof to define a channel therebetween, grinding means disposed in said channel in substantially abutting operative relationship with said body and the inner wall of said casing, means for moving said body relative to said casing, and mounting means for said grinding means effective to cause said grinding means to move along said channel relative to one only of said body and said inner wall of said casing while allowing grinding action between said grinding means and both said body and said inner wall of said casing, whereby when particles are fed into said casing inlet during said relative motion of said body and saidcasing, said grinding means provides a shearing action on said particles.

2. The processing apparatus of claim 1, wherein said casing is cylindrical and wherein said body comprises a shaft rotatably mounted axially in said cylindrical casing, and means to rotate said shaft with respect to said casing.

3. The processing apparatus of claim 2, wherein said shaft is mounted concentrically within said casing.

4. The processing apparatus of claim 2, wherein said grinding means comprises a plurality of axially extending grinding members, at least some of which are substantially contiguous to said shaft and at least some of which are substantially contiguous to said inner wall of said casing.

5. The processing apparatus of claim 4, wherein at least some of said grinding members are disposed within said channel in free floating relationship with said body and said casing.

6. The processing apparatus of claim 5, wherein said mounting means comprises at least one of said grinding members keyed to said shaft.

7. The processing apparatus of claim 4, wherein said mounting means comprises at least one of said grinding members being keyed to said shaft.

8. The processing apparatus of claim 7, wherein said mounting means further comprises a plurality of collars fixedly mounted on and spaced along said shaft, each of said collars having at least one keyway adapted to receive one of said grinding members, thereby to key said one of said grinding members to said shaft.

9. The processing apparatus of claim 8, wherein said collars extend substantially across the width of said channel, thereby separating said channel into a plurality of compartments and wherein said grinding members are disposed within said compartments.

10. The processing apparatus of claim 7, wherein said grinding members comprise rolls of circular cross section and wherein said rolls are disposed in said channel in contiguous relationship.

11. The processing apparatus of claim 10, wherein said mounting means further comprises a plurality of collars fixedly mounted on and spaced along said shaft, each of said collars having at least one keyway adapted to receive one of said grinding members, thereby to key said one of said grinding members to said shaft,

12. The processing apparatus of claim 11, wherein said collars extend substantially across the width of said channel, thereby separating said channel into a plurality of compartments and wherein said grinding members are disposed within said compartments.

13. The processing apparatus of claim 4, wherein said grinding members comprise rolls of circular cross-section and wherein said rolls are disposed in said channel in contiguous relationship with each other.

14. The processing apparatus of claim 8, wherern all of said rolls are of a diameter substantially less than the width of said annular channel, alternate rolls being in substantially contiguous relationship with said shaft and said inner wall of said casing, respectively.

15. The processing apparatus of claim 8, wherein some of said rolls have diameters different from others of said rolls.

16. The processing apparatus of claim 9, wherein every other roll has the same cross-section.

17. The processing apparatus of claim 10, wherein one set of every other rolls have diameters substantially equal to the width of said annular channel and wherein said rolls disposed .contiguously between said one set of every other rolls have diameters substantially less than the width of said annular channel.

18. The processing apparatus of claim 4, wherein said shaft is provided with axially extending arcuate grooves adapted to receive said grinding members, said grooves comprising said mounting means for said grinding means.

19. The processing apparatus of claim 2, wherein said shaft and said casing have cylindrical cross-sections defining therebetween an annular channel of uniform width.

20. The processing apparatus of claim 19, wherein said grinding means *comprisesa plurality of axially extending grinding members, at least some of which are substantially contiguous to said shaft and at least some of which are substantially contiguous to said inner wall of said casing.

21. The processing apparatus of claim 1, further comprising means for feeding said particles axially into said casing.

22. The processing apparatus of claim 21, wherein said grinding means comprises a plurality of axially extending grinding members, at least some of which are substantially contiguous to said body and at least some of which are substantially contiguous to said inner wall of said casing.

l i i I It 

1. A processing apparatus for reducing the size of particles comprising a casing having an inlet and an outlet, a body movably mounted within said casing and spaced from the inner wall thereof to define a channel therebetween, grinding means disposed in said channel in substantially abutting operative relationship with said body and the inner wall of said casing, means for moving said body relative to said casing, and mounting means for said grinding means effective to cause said grinding means to move along said channel relative to one only of said body and said inner wall of said casing whiLe allowing grinding action between said grinding means and both said body and said inner wall of said casing, whereby when particles are fed into said casing inlet during said relative motion of said body and said casing, said grinding means provides a shearing action on said particles.
 2. The processing apparatus of claim 1, wherein said casing is cylindrical and wherein said body comprises a shaft rotatably mounted axially in said cylindrical casing, and means to rotate said shaft with respect to said casing.
 3. The processing apparatus of claim 2, wherein said shaft is mounted concentrically within said casing.
 4. The processing apparatus of claim 2, wherein said grinding means comprises a plurality of axially extending grinding members, at least some of which are substantially contiguous to said shaft and at least some of which are substantially contiguous to said inner wall of said casing.
 5. The processing apparatus of claim 4, wherein at least some of said grinding members are disposed within said channel in free floating relationship with said body and said casing.
 6. The processing apparatus of claim 5, wherein said mounting means comprises at least one of said grinding members keyed to said shaft.
 7. The processing apparatus of claim 4, wherein said mounting means comprises at least one of said grinding members being keyed to said shaft.
 8. The processing apparatus of claim 7, wherein said mounting means further comprises a plurality of collars fixedly mounted on and spaced along said shaft, each of said collars having at least one keyway adapted to receive one of said grinding members, thereby to key said one of said grinding members to said shaft.
 9. The processing apparatus of claim 8, wherein said collars extend substantially across the width of said channel, thereby separating said channel into a plurality of compartments and wherein said grinding members are disposed within said compartments.
 10. The processing apparatus of claim 7, wherein said grinding members comprise rolls of circular cross section and wherein said rolls are disposed in said channel in contiguous relationship.
 11. The processing apparatus of claim 10, wherein said mounting means further comprises a plurality of collars fixedly mounted on and spaced along said shaft, each of said collars having at least one keyway adapted to receive one of said grinding members, thereby to key said one of said grinding members to said shaft.
 12. The processing apparatus of claim 11, wherein said collars extend substantially across the width of said channel, thereby separating said channel into a plurality of compartments and wherein said grinding members are disposed within said compartments.
 13. The processing apparatus of claim 4, wherein said grinding members comprise rolls of circular cross-section and wherein said rolls are disposed in said channel in contiguous relationship with each other.
 14. The processing apparatus of claim 8, wherein all of said rolls are of a diameter substantially less than the width of said annular channel, alternate rolls being in substantially contiguous relationship with said shaft and said inner wall of said casing, respectively.
 15. The processing apparatus of claim 8, wherein some of said rolls have diameters different from others of said rolls.
 16. The processing apparatus of claim 9, wherein every other roll has the same cross-section.
 17. The processing apparatus of claim 10, wherein one set of every other rolls have diameters substantially equal to the width of said annular channel and wherein said rolls disposed contiguously between said one set of every other rolls have diameters substantially less than the width of said annular channel.
 18. The processing apparatus of claim 4, wherein said shaft is provided with axially extending arcuate grooves adapted to receive said grinding members, said grooves comprising said mounting means for said grinding means.
 19. The processing apparatus of claim 2, wherein said sHaft and said casing have cylindrical cross-sections defining therebetween an annular channel of uniform width.
 20. The processing apparatus of claim 19, wherein said grinding means comprises a plurality of axially extending grinding members, at least some of which are substantially contiguous to said shaft and at least some of which are substantially contiguous to said inner wall of said casing.
 21. The processing apparatus of claim 1, further comprising means for feeding said particles axially into said casing.
 22. The processing apparatus of claim 21, wherein said grinding means comprises a plurality of axially extending grinding members, at least some of which are substantially contiguous to said body and at least some of which are substantially contiguous to said inner wall of said casing. 